*Disclaimer: I am a former employee of Cryptic Studios and worked on Champions Online. This article is by no means a critique of their implementation of the system, only a consideration of what it means for games in the future.
Champions Online recently launched, and one of the innovations that it brought to the table was shardlessness - a single server hosting the entire game population. For years, we've played with game populations that were divided across servers into smaller sub-communities. Putting them all together is an interesting idea and one we will no doubt see more of. But, like any innovation It carries some implications to the business and to the community that will no-doubt change things in the MMO space.
Pro: One huge community that can play together. I have a ton of friends who play WoW across different servers. We talk about playing together, but it almost always ends the same: We roll noobs on the server, play maybe a couple of nights in the week and then go back to our mains. We don't have time to essentially play the game over from the start without the resources that our home server provides from our guilds and our mains.
Pro: You'll never have to do server closures. Closing a server on any game is a usually a massive PR hit. I've been through the process, spinning it to contain the most positive message possible. But to the press and the community, closing a server almost always means the same thing: Your game is not as successful as you had projected. For an older game in its twilight years, it almost certainly will bring predictions of doom and total service shutdown.
Con: The savvy number cruncher can gauge the health of your game easily. Even though you'll never have to close a server, one can get a feel for the game's population by making note of the number of instances available and the population per, extrapolating concurrent players to make an educated guess at subscription levels. (This point is a little muddied by the trend toward lifetime subscriptions and free to play business models that we are seeing, but that's another article.)
Pro: Your name is available! One of the biggest problems I had with City of Heroes was that any suitable name was probably already taken. This is less of a problem in fantasy games, where you can string together a series of vowels and consonants to get a decent name (Grognak is already taken? Then how about Brognak), but the super hero genre calls for meaningful names. The shardless system allows duplicate names by appending a global handle after your hero name. I'll never have to worry about Captain Underpants Gnome being taken again!
Con: This is at the expense of privacy. I don't know about you, but I like to get away from my usual posse now and then. I've also been known to break guilds' rules about not having alts in other guilds. As implemented, the shardless system means that others can always find you. Not just your character, but you. Personally, I'm not a role-player, but I'd be curious to learn if RPers out there feel there would be an impact to their gameplay when the global identity has surpassed the character identity.
Con: Server identity and feeling of community are lost. The division of servers gives a natural sense of community, as you can expect to see a consistent set of people when you play and individual guilds begin to define the character of the server. In the past, I've joined guilds mainly because I grouped with a few of their members in PUGs over time and enjoyed it enough to ask to join. Shardlessness means randomness. You can't expect to hook up with the same people all that consistently if they can be on any one of twenty or more instances. I don't add people to my friends list until I've grouped with them a few times, and as a consequence, my Champions friends list currently contains only people I already knew.
I think that the biggest hit here is the sense of identity. In almost every game I have played, certain servers become identified by the unique attributes of its population, whether it is defined by a large base of role-players, the presence of an uber guilds and influential players, or even for being the server where all the douchebags play. The more you become invested in games, the more you base decisions about where you want to play off of information like this.
Overall, I think shardlessness is a good thing, but not a necessity. As long as we are still divided by instances, they won't deliver the feeling of massiveness that one would expect from one shard to rule them all. It's a new option, and I will be interested to see the concept unfold. Communities are resilient, and anything that they lose in the implementation, they'll find a way to make up for, whether on the shard itself or on another channel.